444 



KMllKYOLOGY. 



Fif . 853. Lateral visw of the brain of an embryo Calf 

 6 cm. Ion;. The lateral vail of the hemisphere 

 has been removed. After MIHAI.KOVICS. Magni- 

 fied 8 diameters. 



*, Corpus stria twin ; ML, foramen of MOXRO ; agf, 

 plexus ohoroidens lateral is ; an\f, hippocampal 

 fold ; !*, cerebellum ; Dp, roof of the fourth 

 ventricle; 66, pontal flexure; mo, medulla ob- 

 longata ; mh, mid-brain (parietal flexure). 



(figs. 254 pi and 255 aaf). Instead of thickening and developing 

 mh nerve-substance, it becomes 



attenuated, and is trans- 

 formed into a single layer 

 of flat epithelial cells, which 

 are firmly united with the 

 pia mater. The latter then 

 becomes very vascular along 

 the entire fold, and grows 

 into the lateral ventricle in 

 the form of tufts, which 

 carry the epithelium before 

 them. In this way the 

 lateral choroid plexus arise* 



(fig. 254 pi), which afterwards, in the adult, fills a part of the cella 



media and in- 

 ferior cornu. \ 



It begins at p( 



the foramen of 



MONRO (fig. 



253JHX),where 



it is continuous 



with the an- 

 terior unpaired 



choroid plexus 



which has 



ari>eii in the 



roof of the be- 



tween-brain 



Y>iclo. If the 



delicate \as- 



eularpia mater 



is drawn out 



from the cho- 

 roid fissure, the 



wall of the 



brain, which is 



reduced to a 



thin epithe- 

 lium, is at the 



median wall of 



Fif. 954. Transverse section through the brain of an embryo Sheep 

 27 cm. in length, after Koi IIKVI;. 



The section passes through the region of the foramen of MONRO. 



st, Corpus striatum ; m, foramen of MOXRO ; (, third ventricle ; pi, 

 plexus choroideus of the lateral % outride :/. falx cerebri ; tk, deepest 

 anterior part of the optic thalamus ; c*. chiasma : o, optiv I 



bres of the cms cerebri; A, hippcH-ampal fold : ;', pharynx ; 

 a, preephenoid; a. orlnto sphenoid ; ., part of the ux>f of the 

 brain at the junction of the roof of the third ventricle with the 

 lamina tciininalis; I, lateral ventricle. 



same time destroyed, and there is prodm-ed in the 

 the hemisphere a gaping tisMire. which extends from 



